The computer that sang to its operators
Here's the story told to me by one who was "really there", about the computer that sang to its operators.
The story goes that the night shift of operators on an old Perkin-Elmer mainframe (we are talking late 70s or early 80s here) preferred to play cards than watch the console.
So one geek hooked a wire to the high-order bit on one of the main registers in the CPU (something that was indeed technically possible in the days before chip LSI - in fact some of the register busses may well have been accessible externally) or maybe it was that he got the P-E engineer to do it. They fed it through an amp to a speaker in the "smoko" room. [An Australian-ism for the staff break room.]
They would all sit in there playing cards while the speaker burbled away. It was wired with a switch to shut it up before the bosses arrived in the morning.
This is the days of batch processing at night, so the operators' key task was to ensure the right jobs kicked off in the right sequence.
Apparently they learnt to recognise the "signature" sound of each job. They could check their watch then go back to playing. They quickly recognised a high-pitched continuous tone as a CPU loop! And total silence was bad.
Credible? Just. True? Dunno.